We are requesting funds to purchase the ACAS 570 Interactive Laser Cytometer which is marked by Meridian Instruments of Okemos, MI. This instrument is an integrated fluorescence workstation which is designed for quantitative fluorescence analysis of adherent cells in culture and for interactive applications, such as fluorescence photobleaching to measure diffusion of molecules on or within cells as well s between cells, laser ablation for sorting and selection of anchored cells, and cell surgery for selective removal of organelles or cell processes. The projects described in this Shared Instrumentation Grant will employ various applications of the ACAS protein mobility of cell surfaces, cell-cell communication studies, intracellular Ca2+ and pH measurements of anchorage-dependent cells as well as immunofluorescence staining to obtain both spatial and temporal resolution of various cellular processes and the distribution of specific antigens in neurons, astrocytes, tumor cells, and oncogene- transformed cells. In comparison to flow cytofluorimetric methods and fluorescence-activated cell sorting (FACS), the ACAS system offers three distinct advantages which are necessary for the studies proposed: 1) the ability to analyze and sort anchored cells without having to strip them from their substratum or connecting cells (and possibly causing irreversible and inestimable damage to cellular structure and function); 2) the markers over a prolonged period of time; and 3) the ability to interact with the cells under study (eg., the fluorescence photobleaching applications). Thus, rather than an alternative to the more conventional instruments, the ACAS 570 Interactive Laser Cytometer is complementary to them.